Linxutopia - Thinking in C++ - 16: Introduction to Templates

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Non-inline function definitions

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Of course, there are times when you’ll want to have non-inline member function definitions. In this case, the compiler needs to see the template declaration before the member function definition. Here’s the example above, modified to show the non-inline member definition:

//: C16:Array2.cpp
// Non-inline template definition
#include "../require.h"

template<class T>
class Array {
  enum { size = 100 };
  T A[size];
public:
  T& operator[](int index);
};

template<class T>
T& Array<T>::operator[](int index) {
  require(index >= 0 && index < size,
    "Index out of range");
  return A[index];
}

int main() {
  Array<float> fa;
  fa[0] = 1.414;
} ///:~

Any reference to a template’s class name must be accompanied by its template argument list, as in Array<T>::operator[]. You can imagine that internally, the class name is being decorated with the arguments in the template argument list to produce a unique class name identifier for each template instantiation.

Thinking in C++
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